Catalytic ignition system

ABSTRACT

An improved catalytic pilot ignition system which utilizes a short-circuited, air-starved, electrochemical cell or battery comprising a metal electrode and an inert electrode, such as zinc and carbon electrodes, or metal-air battery such as a zinc-air battery, which will produce a small but sufficient flow of pure hydrogen gas. When such a battery is short-circuited, the current often rises to a level above that which can be supplied with atmospheric air. When this happens, hydrogen is evolved. The evolution of hydrogen ceases immediately when the short-circuited current is interrupted. If a zinc-air battery is operated without access to the air, any current drawn from the cell will produce hydrogen at the air electrode.

United States Patent [191 I Gregory [451 Sept. 30, 1975 CATALYTICIGNITION SYSTEM [75] Inventor: Derek P. Gregory, Hinsdale. Ill.

[73] Assignec: Institute of Gas Technology,

Chicago, Ill.

[22] Filed: May 3, 1974 [211 Appl. No.: 466,683

[52] US. Cl. 431/268; 48/l96; 204/129 [51] Int. Cl. F23Q 11/04 [58]Field of Search 431/268, 2; 48/196; 204/129 [56] References Cited UNITEDSTATES PATENTS 180,588 8/1876 Hufeland et al. 431/268 3.518.036 6/1970Staats et al. 431/268 Primary livuminer-Edward G. Favors Attorney,Agent. or FirmDominik, Knechtel, Godula & Demeur 5 7 ABSTRACT Animproved catalytic pilot ignition system which utilizes ashort-eircuited, air-starved, electrochemical cell or battery comprisinga metal electrode and an inert electrode, such as zinc and carbonelectrodes, or metal-air battery such as a zinc-air battery, which willproduce a small but sufficient flow of pure hydrogen gas. When such abattery is short-circuited, the current often rises to a level abovethat which can be supplied with atmospheric air. When this happens,hydrogen is evolved. The evolution of hydrogen ceases immediately whenthe short-circuited current is interrupted. If a zinc-air battery isoperated without access to the air, any current drawn from the cell willproduce hydrogen at the air electrode.

25 Claims, 2 Drawing Figures CATALYTIC IGNITION SYSTEM This inventionrelates to an improved ignition pro cess for ignition of gas-fueledappliances.

Conventional ignition systems for gas-fueled commercial and residentialappliances generally rely upon standing pilots, electrically heatedwires (glow coils) or spark-generating devices. Standing pilotscontinually consume fuel gas and are unattractive from the standpointsof operating expense, energy conservation and maintenance. Anonymous aircurrents, liquid spills or fuel supply interruptions require pilotrelighting, and unlit pilots constitute a hazard when undetected. Asafety shut-off device must be incorporated into the pilot system foruntended burners. Furthermore, nitrogen oxides emissions from standingpilots in enclosed living areas are becoming a concern because of recentenvironmental and health studies. Spark ignition and glow coil systemsovercome some of these problems, but spark generators are expensive andglow coils have not proven reliable. Moreover, ignition delay problemshave been reported for some glow coil and spark systems. Ignition delaycan be a serious problem in large commercial burners, in forced-draftfurnaces and in confined or restricted volume combustion chambers, andit can be an annoyance on open, natural draft burners.

In US. Pat. No. 3,518,036, issued June, 1970, there is disclosed anelectrically controlled electrolysis cell that furnishes hydrogen andoxygen to a methane pilot stream. The pilot stream then is ignited by acold solid catalyst affixed in operative relationship to a gas pilot,which in turn, ignites a burner. Oxygen enhances the hydrogen reactionat the catalyst surface. Control and switching devices are provided toenergize and deenergize the electrolytic cell and to control the flow ofgases to the catalyst surface and pilot. The major components of thesystem are an AC power source, a transformer, a rectifier, the sealedelectrolysis cell with electrodes and liquid electrolyte, pilot gastubing, the catalyst surface and an electrical switch for operating theelectrolysis cell and gas flow to the gas burner.

The present invention relates to an improved catalytic pilot ignitionsystem providing simplifications and better economics than the abovesystem. The system is based on a short-circuited, air-starved,electrochemical cell or battery comprising a metal electrode and aninert electrode, such as zinc and carbon electrodes, or

metal-air battery, such as a zinc-air battery, which will produce asmall but sufficient flow of pure hydrogen gas. More particularly, whensuch a battery is short circuited, the current often rises to a levelabove that which can be supplied with atmospheric air. When thishappens, hydrogen is evolved. The evolution of hydrogen ceasesimmediately when the short-eircuit current is interrupted. If a zinc-airbattery is operated without access to the air, any current drawn fromthe cell will produce hydrogen at the air electrode.

in accordance with the present invention, the battery is placed in asealed container with a small capillary tube leading to a burner port orports. At the end of the capillary tube is placed a catalytic surface,such as platinum black. When the gas valve is turned on, the battery isshort-circuited, and a burst of hydrogen flows down the tube and igniteson the catalyst. If desired, a suitable circuit can be provided tosensewhether the gas burner is lit and immediately interrupt the circuit onthe battery so that the battery life is conserved.

Accordingly, it is an object of the present invention to provide animproved apparatusandignition process for igniting gas-fueledappliances.

Other objects of the invention will in part be obvious and will in partappear hereinafter.

For a fuller understanding of the nature ,and objects of the invention,reference should be had to the following detailed description taken inconnection with the accompanying drawings, in which:

FIG. 1 is a diagrammatic view generally illustrating the constructionand electrical circuitry of an exemplary pilot ignition system; and

FIG. 2 is a diagrammatic view illustrating an alternative arrangement ofthe electrical circuitry thereof.

Similar reference characters refer to similar parts throughout theseveral views of the drawings.

Referring now to the drawings, the catalytic pilot ignition system canbe seen to include a battery 10 which is disposed within a sealedcontainer 12. The battery 10 may be an electrochemical battery having ametal electrode l1 and an inert electrode 13, such as, for example, azinc electrode and a carbon electrode which when short-circuited andair-starved will evolve hydrogen. Alternatively, the battery 10 may be ametal-air battery, such as, for example, a zinc-air, aluminum-air,sodium-air, potassium-air, iron-air, or any metal having a higherelectrochemical potential then hydrogen. A specific example of azinc-air battery which can be used is the METAIR battery of the typemanufactured and sold by the Energy Conversion Limited, Basingstoke,Hampshire, England, or its equivalent.

The catalytic pilot ignition system further includes a main gas burner16 which is coupled to a main burner gas supply line 18 which is coupledto a source of natural gas (not shown). The supply line 18 includes acontrol valve 20 which is operative to control the flow of.

natural gas to the main gas burner 16, and which is coupled to andoperative to open and close the normally open switch 30. The controlvalve 20 has three positions, an off position, an ignition position anda burner position. When in its off position, the flow of natural gas tothe main gas burner 16 is cut off and the switch 30 is opened. When itis operated to the ignition position, natural gas is permitted to flowto the main gas burner 16, and the switch 30 is closed to cause ignitionof the main gas burner 16, in the manner described below. Afterignition, the control valve 20 is operated to its normal operatingposition and, in this position, the flow of natural gas continues, butthe switch 30 is again opened.

A catalyst 40 is positioned with respect to the main gas burner 16 suchthat the gas flowing from it is impinged upon the catalyst 40. It isgenerally well-known that some catalysts are adversely effected by theheat or some combustion products. If the particular catalyst used is ofthis nature, it should be properly protected. This may be accomplishedin several suitable fashions. for example, by affixing the catalyst 40to a bimetallic element which upon being heated, is adapted to move thecatalyst out of the pilot flame.

-A capillary tube 14, or the like, is coupled with the battery 10 and isextendedto the catalyst 40, so that hydrogen produced by the batteryflows down the tube 14 and is ignited on'the catalyst 40.

The operation of the catalytic ignition system can be generallydescribed as follows. Control valve 20 is manually operated to itsignition position, to permit natural gas to flow to the main gas burner16 and to close the normally opened switch 30. When switch 30 closes,the battery is short circuited, and a burst of hydrogen flows down thecapillary tube 14 and ignites on the catalyst 40.

Once the main gas burner 16 is ignited, the control valve 20 is operatedto its burner position, which operation opens the switch 30 and hencethe short circuit on the battery 10. When the short circuit on thebattery is interrupted, the generation and flow of hydrogen through thecapillary tube 14 to the catalyst 40 is stopped. The main burner flame,however, remains lit. By interrupting the short circuit on the battery,once the main gas burner 16 is ignited, battery life is conserved.

To turn off the main gas burner 16, the control valve 20 is merelyoperated to its off position. In this position, the switch 30 remainsopen and the short circuit on the battery is interrupted.

An alternative electrical circuit is illustrated in FIG. 2. In thiscircuit, a temperature sensor 50 is affixed in close proximity to themain gas burner 16 and is adapted to open a normally closed switch 52when the main gas burner 16 ignites, to interrupt the short circuit onthe battery 10. The temperature sensor 50 can be and preferably iscoupled to and adapted to operate a conventional flame safety valve, inthe event the gas burner fails to ignite or is blown out or otherwiseextinguished. The normally closed switch 52 is connected in a seriescircuit with the switch 30 which functions to short circuit the battery10. The control valve 20, in this case, also can be merely a twoposition valve, having an off position and a burner position, since theswitch 52 functions to open the short circuit on the battery l0. ln allother respects, the ignition system operates in the above-describedfashion.

The catalyst 40 can be any catalyst that is active with hydrogen, suchas, for example, platinum or palladium. The catalyst 40 can be affixedto a refractory surface such as alumina, silica, zirconia, thoria, anymixture of refractory materials, and even metals, such as platinumitself, if desired. Furthermore, it is generally wellknown that somecatalyst will cause reaction to proceed faster and will heat up to atemperature sufficient to ignite the gas mixture (the natural gas andhydrogen) quicker than others when hydrogen is impinged on them. Thisreaction rate also is dependent on numerous other factors, such as thesurface area of the catalyst, the orifice size and the flow rate of thegas mixture, to mention but a few of them. Accordingly, once thecatalyst is selected, the required orifice size, the flow rate of thegas mixture and the proper proportion of natural gas and hydrogen toprovide ignition can be determined experimentally.

It will thus be seen that the objects set forth above among those madeapparent from the preceding description, are efficiently attained andcertain changes may be made in carrying out the above process and in theconstruction set forth. Accordingly, it is intended that all mattercontained in the above description or shown in the accompanying drawingsshall be interpreted as illustrative and not in a limiting sense.

Now that the invention has been described, what is claimed as new anddesired to be secured by Letters Patent is:

1. In combination with a catalytic pilot ignition system having a gasburner coupled to a source of natural gas, control valve means forcontrolling the flow of natural gas from the source to the burner, and acatalyst active with hydrogen positioned with respect to the gas burnerto ignite the natural gas flowing from the source to the gas burner whenhydrogen is impinged on the catalyst, the improvement comprising ashort-circuited, air starved, battery for producing the hydrogenimpinged on said catalyst.

2. The combination of claim 1, wherein said battery comprises anelectrochemical battery having a metal electrode and an inert electrodewhich when shortcircuited and air-starved evolves hydrogen.

3. The combination of claim 2, wherein said electrochemical batterycomprises a zinc electrode and a carbon electrode.

4. The combination of claim 1, wherein said battery comprises ametal-air battery.

5. The combination of claim 4, wherein said metal-air battery comprisesa zinc-air battery.

6. The combination of claim 4, wherein said metal-air battery comprisesan aluminum-air battery.

7. The combination of claim 4, wherein said metal-air battery comprisesa sodium-air battery.

8. The combination of claim 4, wherein said metal-air battery comprisesa potassium-air battery.-

9. The combination of claim 4, wherein said metal-air battery comprisesa iron-air battery.

10. The combination of claim 4, wherein said metalair battery comprisesany metal having a higher electrochemical potential than hydrogen.

11. The combination of claim 1, further including means for interruptingthe short-circuit on the battery.

12. The combination of claim 1, further including contact means operatedby said control valve means to short-circuit said battery only when saidcontrol valve means is operated to direct a flow of natural gas fromsaid source to said burner.

13. The combination of claim 3, wherein said control valve means isfurther operable to interrupt the shortcircuit on said battery and tomaintain the flow of natural gas from said source to said burner whenthe natural gas is ignited.

14. The combination of claim 3, further including means for interruptingthe short-circuit on said battery when said natural gas flowing to saidburner is ignited.

15. The combination of claim 5, wherein said means for interrupting theshort-circuit on said battery comprises a normally closed contact andtemperature sensing means operable to open said normally closed contact.

16. A catalytic pilot ignition system for igniting natural gascomprising, in combination: a gas burner coupled to a source of naturalgas; control valve means for controlling the flow of natural gas fromsaid source to said burner; a catalyst active with hydrogen positionedwith respect to said gas burner such that hydrogen impinged on saidcatalyst is ignited and in turn ignites natural gas flowing from saidburner, a metal-air battery within a sealed container having tube meansextending therefrom to impinge hydrogen produced by said metal-airbattery on said catalyst; and means for shortcircuiting said metal-airbattery to produce hydrogen.

17. The system of claim 16, wherein said means for short-circuiting saidmetal-air battery comprises contact means operated by said control valvemeans.

18. The combination of claim 17, wherein said control valve means isfurther operable to interrupt the short-circuit on said metal-airbattery and to maintain the flow of natural gas from said source to saidburner when the natural gas is ignited.

19. The combination of claim 17, further including means forinterrupting the short-circuit on said metalair battery when saidnatural gas flowing to said burner is ignited.

20. The combination of claim 19, wherein said means for interrupting theshort-circuit on said metal-air battery comprises a normally closedcontact and temperature sensing means operable to open said normallyclosed contact.

21. A catalytic pilot ignition system for igniting natural gascomprising, in combination: a gas burner coupled to a source of naturalgas; control valve means for controlling the flow of natural gas fromsaid source to said burner; a catalyst active with hydrogen positionedwith respect to said gas burner such that hydrogen impinged on saidcatalyst is ignited and in turn ignites natural gas flowing from saidburner, an electrochemical battery having a metal electrode and an inertelectrode within a sealed container having tube means extendingtherefrom to impinge hydrogen produced by said electrochemical batteryon said catalyst;.and means for short-circuiting said electrochemicalbattery to produce hydrogen.

22. The system of claim 21, wherein said means for short-circuiting saidelectrochemical battery comprises contact means operated by said controlvalve means.

23. The combination of claim 22, wherein said control valve means isfurther operable to interrupt the short-circuit on said electrochemicalbattery and to maintain the flow of natural gas from said source to saidburner when the natural gas is ignited.

24. The combination of claim 22, further including means forinterrupting the short-circuit on said electrochemical battcry when saidnatural gas flowing to said burner is ignited.

25. The combination of claim 24, wherein said means for interrupting theshort-circuit on said electrochemical battery comprises a normallyclosed contact and temperature sensing means operable to open saidnormally closed contact. 4

1. IN COMBINATION WITH A CATALYTIC PILOT IGNITION SYSTEM HAVING A GASBUTNER COUPLED TO A SOURCE OF NATURAL GAS, CONTROL VALVE MEANS FORCONTROLING THE FLOW OF NATURE GAS FROM THE SOURCE TO THE BURNER, AND ACATALYST ACTIVE WITH HYDROGEN POSITIONED WITH RESPECT TO THE GAS BURNERTO IGNITE THE NATURAL GAS FLOWING FROM THE SOURCE TO THE GAS BURNER WHENHYDROGEN IS IMPINGED ON THE CATALYST, THE IMPROVEMENT COMPRISING ASHORT-CIRCUITED, AIR STARVED, BATTERY FOR PRODUCING THE HYDROGENIMPINGED ON SAID CATALYST.
 2. The combination of claim 1, wherein saidbattery comprises an electrochemical battery having a metal electrodeand an inert electrode which when short-circuited and air-starvedevolves hydrogen.
 3. The combination of claim 2, wherein saidelectrochemical battery comprises a zinc electrode and a carbonelectrode.
 4. The combination of claim 1, wherein said battery comprisesa metal-air battery.
 5. The combination of claim 4, wherein saidmetal-air battery comprises a zinc-air battery.
 6. The combination ofclaim 4, wherein said metal-air battery comprises an aluminum-airbattery.
 7. The combination of claim 4, wherein said metal-air batterycomprises a sodium-air battery.
 8. The combination of claim 4, whereinsaid metal-air battery comprises a potassium-air battery.
 9. Thecombination of claim 4, wherein said metal-air battery comprises airon-air battery.
 10. The combination of claim 4, wherein said metal-airbattery comprises any metal having a higher electrochemical potentialthan hydrogen.
 11. The combination of claim 1, further including meansfor interrupting the short-circuit on the battery.
 12. The combinationof claim 1, further including contact means operated by said controlvalve means to short-circuit said battery only when said control valvemeans is operated to direct a flow of natural gas from said source tosaid burner.
 13. The combination of claim 3, wherein said control valvemeans is further operable to interrupt the short-circuit on said batteryand to maintain the flow of natural gas from said source to said burnerwhen the natural gas is ignited.
 14. The combination of claim 3, furtherincluding means for interrupting the short-circuit on said battery whensaid natural gas flowing to said burner is ignited.
 15. The combinationof claim 5, wherein said means for interrupting the short-circuit onsaid battery comprises a normally closed contact and temperature sensingmeans operable to open said normally closed contact.
 16. A catalyticpilot ignition system for igniting natural gas comprising, incombination: a gas burner coupled to a source of natural gas; controlvalve means for controlling the flow of natural gas from said source tosaid burner; a catalyst active with hydrogen positioned with respect tosaid gas burner such that hydrogen impinged on said catalyst is ignitedand in turn ignites natural gas flowing from said burner, a metal-airbattery within a sealed container having tube means extending therefromto impinge hydrogen produced by said metal-air battery on said catalyst;and means for short-circuiting said metal-air battery to producehydrogen.
 17. The system of claim 16, wherein said means forshort-circuiting said metal-air battery comprises contact means operatedby said control valve means.
 18. The combination of claim 17, whereinsaid control valve means is further operable to interrupt theshort-circuit on said metal-air battery and to maintain the flow ofnatural gas from said source to said burner when the natural gas isignited.
 19. The combination of claim 17, further including means forinterrupting the short-circuit on said metal-air battery when saidnatural gas flowing to said burner is ignited.
 20. The combination ofclaim 19, wherein said means for interrupting the short-circuit on saidmetal-air battery comprises a normally closed contact and temperaturesensing means operable to open said normally closed contact.
 21. Acatalytic pilot ignition system for igniting natural gas comprising, incombination: a gas burner coupled to a source of natural gas; controlvalve means for controlling the flow of natural gas from said source tosaid burner; a catalyst active with hydrogen positioned with respect tosaid gas burner such that hydrogen impinged on said catalyst is ignitedand in turn ignites natural gas flowing from said burneR, anelectrochemical battery having a metal electrode and an inert electrodewithin a sealed container having tube means extending therefrom toimpinge hydrogen produced by said electrochemical battery on saidcatalyst; and means for short-circuiting said electrochemical battery toproduce hydrogen.
 22. The system of claim 21, wherein said means forshort-circuiting said electrochemical battery comprises contact meansoperated by said control valve means.
 23. The combination of claim 22,wherein said control valve means is further operable to interrupt theshort-circuit on said electrochemical battery and to maintain the flowof natural gas from said source to said burner when the natural gas isignited.
 24. The combination of claim 22, further including means forinterrupting the short-circuit on said electrochemical battery when saidnatural gas flowing to said burner is ignited.
 25. The combination ofclaim 24, wherein said means for interrupting the short-circuit on saidelectrochemical battery comprises a normally closed contact andtemperature sensing means operable to open said normally closed contact.